Around mile 10 of a recent half marathon, my quadriceps started to
tighten and my feet increasingly felt like lead. Along with improving my
training, perhaps in the future I will use zinc-finger nuclease
scissors to snip out a gene called IL-15Rα, so I can run long distances
with ease.

Mice that lack this gene, which is related to muscle contraction, can run much farther than their counterparts, a new study says — suggesting a genetic predisposition to endurance in some athletes.

Physiologists
led by Tejvir Khurana at the University of Pennsylvania were studying
IL-15Rα, which had been linked to proteins associated with muscle
contraction. They engineered mice to lack that gene, and recorded the
mice’s activity. Every night, the knockout mice ran six times farther
than normal mice, according to the Science NOW blog.

The team dissected the muscles in these marathon mice, and found the
muscles had more fibers and more mitochondria, the power plants of
cells, Science NOW reports. This meant the muscles took longer to tire
and longer to use up their energy supplies. The researchers found that
the lack of IL-15Rα coaxed one type of muscle cell to turn into another
type — from fast-twitch, easily tired muscles into slower-contracting,
longer-endurance muscles.